# Getting all promoters of a specific gene

I'd like to perform a motif analysis of all promoter regions of the gene ENSMUSG00000020538 in mus musculus. To do so, I wanted to use Biomart :

library('biomaRt')
mart <- useMart("ensembl")
mart <- useDataset("mmusculus_gene_ensembl", mart = mart)
all.genes <- getSequence(id = 'ENSMUSG00000020538',
type="ensembl_gene_id",
seqType="coding_gene_flank",
upstream=100,
mart=mart)


But this provide me only the flanking region of the sepcified gene, not all its promoter regions. How could I do ?